The basic thrust of this proposal is to assess the various membrane ATPase activities present in vascular smooth muscle which may be involved in ion regulation. To accomplish this, we will study the contents of at least 2 different membrane fractions, a heterogeneous microsomal fraction and a detergent prepared membrane fraction. Enzyme activities to be examined are: Ca ions-ATPase, Mg ions-ATPase, Ca ions plus K ion-ATPase, Na ion-ATPase, K ion-ATPase and Na ion, K ion-ATPase (ouabain inhibited). Their presence has already been identified in the microsomal fractions, but no specific roles have as yet been identified. In the detergent prepared membrane fraction, ouabain inhibited Na ion,K ion-ATPase is predominant, and a detailed study of this enzyme's characteristics may be important to understanding the potential sarcolemmal role in Ca ions regulation. The assessment of these various enzyme activities will be correlated to various "functional" aspects of the preparations such as a energy-dependent Ca ions sequestration and possible Na ion, Ca ions-exchange. It is hoped that such an approach will identify the relationship between the various ATPases and regulation of contractility in vascular smooth muscle, and help to elucidate the mechanisms controlling pharmacologic heterogeneity.